Proton Therapy (PT) is a cancer treatment technology that uses high energy protons to penetrate a patient's body and deposit energy into treatment areas such as cancerous tumors. PT systems commonly implement a rotating gantry wheel that directs the proton beam to the patient from any angle between zero and 360 degrees. This allows the physician to design a treatment plan that attacks cancerous tumors from different angles and reduces radiation damage to critical organs and/or healthy tissue.
One of the challenges facing PT systems is to maintain proper alignment between the proton delivery nozzle and the isocenter of the rotating gantry system when the gantry is rotated to different treatment angles. For example, it is desirable to maintain accuracy of the proton beam to the gantry center in order to accurately focus the proton beam to a targeted area of interest. Due to inherent fabrication tolerances and the extreme size and weight of the gantry apparatus and its various components, the structure can deflect when rotated at different angles, allowing the system's center to drift above the target accuracy.
It is known to move the patient bed to compensate for subtle drifts in the system at different angles of rotation. However, moving the patient to compensate for beam misalignment can become quite time consuming and complicated, especially if the treatment plan requires more than one application angle for each patient. Therefore, it would be desirable to align the gantry apparatus itself in anticipation of the deviances that occur through rotation of the gantry apparatus.
Another challenge facing PT systems is the time it takes to construct and implement a working system. For example, it typically takes about 6 months to build a gantry on site and an additional 12 months to commission the equipment. This lengthy build time is largely associated with the size of the magnets required to direct protons through the gantry and the related beam accuracy demands.